The invention relates to a method for organizing a network of communicating objects.
A network of communicating objects may be formed by a plurality of communicating objects able to communicate with each other directly in an ad hoc manner, without passing through a base station or a centralized server, generally using inexpensive wireless communication technologies. They can be static communicating objects (office computer) or mobile communicating objects (laptop, PDA, sensor, cell phone, etc.).
Such a network can be created spontaneously and has no previously defined topology. Neither address servers nor routers are preconfigured for address allocation and message routing. After deployment, the network of objects is self-configured and self-organized dynamically, in a phase for putting into place communications. Non-limiting examples of such networks might include networks of sensors or even home networks.
The self-configuration of the network is aimed mainly at allocating addresses to the nodes of the network, whereas the self-organization is aimed at organizing the infrastructure of the network, at structuring it, by defining the respective roles of the various nodes of the network, in order to enhance the efficiency of the communications and to facilitate the implementation of the services. The prefix “self” refers to a process carried out by the nodes of the network themselves, without intervention from any source external to the network.
Self-configuration and self-organization are two separate mechanisms. Ordinarily, the self-configuration precedes the self-organization: when a network is formed, initially, the nodes implement a dynamic address allocation algorithm to configure their network interfaces then, secondly, they participate in a general organization of the network, more often than not based on the previously configured addresses. The address allocation mechanism must primarily guarantee the uniqueness of each of the node addresses in the network as a whole.
There are various approaches for allocating addresses in a network of communicating objects. One of these approaches, described in the documents P. Patchipulusu. Dynamic address allocation protocols for mobile ad hoc networks. Master's thesis, Texas A&M University, 2001, and Y. Sun and E. Belding-Royer. Dynamic address configuration in mobile ad hoc networks. Technical Report, University of California, June 2003, is based on leader nodes: one or more leader nodes of the network are responsible for allocating or registering addresses and ensure the uniqueness of the addresses throughout the network. Where there is a plurality of leader nodes, the latter synchronize, in a distributed way, the information on the allocated addresses and/or on the available addresses.
In an ad hoc network of communicating objects, the self-organization protocol must be implemented in a distributed way on the nodes. Each node takes a local decision after having collected local information. These local decisions culminate in a global organization having the desired properties.
There are, in particular, self-organization protocols based on the construction of “clusters”, in other words, communication groups. In each group, a group leader is responsible for specific functionalities for all the communicating objects of the group. Generally, the elected group leader corresponds to the one having the lowest identifier, as is described in the document A. Ephremides, J. Wieselthier and D. Baker. A design concept for reliable mobile radio networks with frequency hopping signalling. Proc of the IEEE, 75(1):56-73, 1987. This type of self-organization protocol therefore requires the self-configuration to have been performed before all the nodes start electing the group leaders in the network.
Implementing the initial phase of self-configuration and of self-organization of a network of communicating objects entails the sending and receiving by the latter, more often than not by airwaves, of a large quantity of data. This is accompanied by a huge energy expenditure. As an illustration, some sensors use up as much as half of their battery in this initial phase. The critical point in the development of networks of communicating objects essentially lies in the energy longevity of the communicating objects. One of the pathways for growth of the networks of communicating objects consequently involves the development and use of self-configuration and self-organization mechanisms that use up less electricity, in order to increase the energy autonomy of the communicating objects, which is what the present invention provides.